Electron beam melting composite grinding method for improving surface finish of high carbon steel

Abstract

The present application relates to the technical field of metal surface modification, and particularly relates to an electron beam melting composite grinding method capable of improving the surface smoothness of high-carbon steel, which comprises the following steps: step one, installing a grinding and polishing rod; step two, placing a high-carbon steel sample on a loading platform; step three, vacuumizing; step four, aiming an electron beam gun head at the corners of the high-carbon steel sample and lowering the height of the grinding and polishing rod; step five, starting the electron beam emitting device and the grinding and polishing rod; step six, controlling the horizontal movement of the loading platform to realize horizontal polishing and grinding; step seven, adjusting the positions of the electron beam gun and the grinding and polishing rod so that the electron beam gun is directly opposite the unpolished and ungrounded part of the high-carbon steel sample; step eight, starting the electron beam emitting device and the grinding and polishing rod; and step nine, repeating steps six to eight to complete the polishing and grinding treatment.The present application has the beneficial effect that it is suitable for steel materials with high hardness and can realize mirror polishing without removal and zero loss through the mode of first melting and then liquid polishing.

Description

Technical Field

[0001] This invention relates to the field of metal surface modification technology, and in particular to an electron beam melting composite grinding method that can improve the surface finish of high carbon steel. Background Technology

[0002] High-carbon steel, due to its high hardness and thermal stability, is commonly used in molds, automotive parts, and bridges. However, surface finishing of high-carbon steel is a crucial step in parts manufacturing. Because of its high hardness, conventional mechanical polishing methods are inefficient and difficult. Furthermore, they require high-hardness abrasives, and the dust generated during machining poses a significant hazard to operators. While mechanical polishing has these drawbacks, it reduces the surface roughness to Ra of 0.5 μm after polishing.

[0003] Electron beam polishing is a non-contact surface treatment method that uses a high-energy electron beam to bombard the metal surface, causing it to melt and thus creating a "self-polishing" effect. This method is a thermal polishing process that can overcome the barriers of mechanical polishing to grinding tools. However, the "self-polishing" effect formed by the combined action of gravity and surface tension of the molten metal is relatively limited. After electron beam polishing, the surface roughness of high-carbon steel can only be reduced to about 1.5 μm, which cannot achieve the surface roughness effect achieved by mechanical polishing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an electron beam melting composite grinding method that can improve the surface finish of high carbon steel, so as to solve the above-mentioned problems existing in the prior art and obtain high carbon steel with a high surface finish.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: An electron beam melting composite grinding method that can improve the surface finish of high carbon steel includes the following steps:

[0006] Step 1: Install a polishing rod on the rear side of the electron beam gun in the electron beam cavity via a lifting mechanism, and install a rotary drive mechanism for driving the polishing rod to rotate axially in the vertical direction.

[0007] Step 2: Place the high carbon steel sample to be ground on the stage inside the electron beam cavity, and then tighten the stage fixture to fix the high carbon steel sample.

[0008] Step 3: Use a vacuum pump to evacuate the vacuum chamber of the electron beam machine;

[0009] Step 4: Adjust the observation window to align the electron beam gun tip with the corner of the high-carbon steel sample, and simultaneously lower the height of the polishing rod.

[0010] Step 5: Set the parameters for the electron beam machine, turn on the electron beam emitting device, and simultaneously rotate the polishing rod at high speed.

[0011] Step 6: Adjust the horizontal movement of the stage along the X-axis to achieve horizontal polishing. The polishing rod rotates and polishes the polished part of the high-carbon steel sample.

[0012] Step 7: After the polishing of a section of the high carbon steel sample in the X-axis direction is completed, raise the polishing bar, the stage moves the high carbon steel sample back to its original position, and then the stage moves the high carbon steel sample in the Y-axis direction so that the electron beam gun is facing the edge of the unpolished part of the high carbon steel sample, and lower the height of the polishing bar.

[0013] Step 8: Turn on the electron beam emitting device and simultaneously rotate the polishing rod at high speed.

[0014] Step 9: Repeat steps 6 to 8 to complete the polishing and grinding of the entire upper surface of the high-carbon steel sample.

[0015] The beneficial effects of this invention are: This invention first uses a high-energy-density electron beam to melt the surface of a high-hardness sample, and then uses a high-speed rotating polishing rod to fully fill the depressions with the molten metal in a micro-molten state. The surface finish of the sample after polishing is much higher than that after electron beam polishing. It is suitable for steel materials with high hardness. By melting first and then polishing in liquid state, a mirror polishing effect with zero removal and zero loss can be achieved.

[0016] Based on the above technical solution, the present invention can be further improved as follows.

[0017] Furthermore, in step one, the polishing rod assembly is a hollow polishing rod assembly, which is equipped with a knob to seal its inner cavity. Before clamping the polishing rod, the polishing rod knob is unscrewed, liquid dry ice is injected into its interior, and then the polishing rod knob is tightened.

[0018] The beneficial effects of adopting the above-mentioned further scheme are: the polishing rod is hollow and filled with dry ice, which allows for rapid solidification of liquid metal during polishing by relying on high supercooling, achieving 10 6 -10 8 The cooling rate of ℃ / s significantly refines the grains on the sample surface.

[0019] Furthermore, in step two, before placing the high-carbon steel sample to be ground on the stage inside the electron beam cavity, the high-carbon steel sample to be ground is pretreated. The pretreatment includes: using a wire cutting device to process the high-carbon steel sample to be ground into a cubic block shape, and immersing the high-carbon steel sample in kerosene to clean it and remove various residual oil stains from the surface.

[0020] The beneficial effect of adopting the above-mentioned further scheme is that the high carbon steel to be ground is processed into a cubic high carbon steel sample, which makes it easier to use the same electron beam machine to achieve grinding of all six sides of the high carbon steel sample.

[0021] Furthermore, in step three, the vacuum level of the electron beam machine vacuum chamber is 6 × 10⁻⁶. -2 Pa.

[0022] The beneficial effect of adopting the above-mentioned further solution is to ensure the vacuum level during the electron beam polishing process, thereby ensuring the polishing effect.

[0023] Furthermore, in step one, the distance between the polishing rod and the electron beam gun head is 1.2-1.5 times the diameter of the lower electron beam.

[0024] The beneficial effect of adopting the above-mentioned further scheme is that maintaining a suitable distance between the polishing rod and the electron beam gun head can ensure that when the polishing rod polishes the surface of the high carbon steel sample that has been melted by the electron beam, the surface of the high carbon steel sample is still in a certain molten state, thus ensuring the polishing effect.

[0025] Furthermore, in step one, the lifting mechanism is installed inside the electron beam cavity via an XY-axis moving mechanism.

[0026] The beneficial effect of adopting the above-mentioned further solution is that the lifting mechanism is installed at the top of the electron beam cavity through the XY axis moving mechanism and is located next to the electron beam gun head, which can conveniently adjust the distance between the polishing rod and the electron beam gun head according to the needs of parameters such as the lower diameter of the electron beam.

[0027] Furthermore, in step five, the electron beam machine is set with the following parameters: electron beam accelerating voltage of 60kV, focusing current of 390mA, accelerating current of 3-7mA, beam spot diameter of 5mm, and stage horizontal moving speed of 3-5mm / s.

[0028] Furthermore, in steps five, six, and eight, the rotation speed of the polishing rod is 300-500 r / min.

[0029] The beneficial effect of adopting the above-mentioned further solution is that by using the above parameters, the polishing effect can be ensured, so that the surface roughness Ra after polishing can be less than 0.1μm. Attached Figure Description

[0030] Figure 1 This is a flowchart of the present invention;

[0031] Figure 2 This is a schematic diagram of the polishing and grinding process of the present invention;

[0032] Figure 3 This is a schematic diagram showing the positions of the polishing rod and the beam spot during the polishing and grinding process of this invention;

[0033] The attached diagram lists the components represented by each number as follows:

[0034] 1. Stage; 2. High-carbon steel sample; 3. Electron beam gun; 4. Polishing rod; 5. Beam spot. Detailed Implementation

[0035] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0036] like Figure 1 , Figure 2 As shown, embodiments of the present invention include the following steps:

[0037] Step 1: A polishing rod 4 is installed on the rear side of the electron beam gun 3 in the electron beam cavity via a lifting mechanism. The lifting mechanism is installed in the electron beam cavity via an XY axis moving mechanism, and a rotary drive mechanism for driving the polishing rod 4 to rotate axially in the vertical direction is installed on the lifting mechanism.

[0038] Step 2: Pre-treatment of the high carbon steel sample 2 to be ground. The pre-treatment includes: using a wire cutting device to process the high carbon steel to be ground into a cubic block shape, and immersing the high carbon steel sample 2 in kerosene to clean it and remove various residual oil stains on the surface; after the pre-treatment is completed, the high carbon steel sample 2 to be ground is placed on the stage 1 inside the electron beam cavity, and then the fixture of the stage 1 is tightened to fix the high carbon steel sample 2.

[0039] Step 3: Use a vacuum pump to evacuate the electron beam machine's vacuum chamber to a vacuum level of 6 × 10⁻⁶. -2 Pa;

[0040] Step 4: Adjust the observation window to align the electron beam gun 3 head with the corner of the high carbon steel sample 2, and simultaneously lower the height of the polishing rod 4.

[0041] Step 5: Set the parameters for the electron beam machine, turn on the electron beam emitting device, and simultaneously rotate the polishing rod 4 at high speed.

[0042] Step 6: Adjust the stage 1 to move horizontally along the X-axis to achieve horizontal polishing. The polishing rod 4 rotates and polishes the polished part of the high carbon steel sample 2.

[0043] Step 7: After the polishing of a section of the high carbon steel sample 2 in the X-axis direction is completed, the polishing rod 4 is raised, the stage 1 drives the high carbon steel sample 2 back to its original position, and then the stage 1 drives the high carbon steel sample 2 to move in the Y-axis direction so that the electron beam gun 3 is facing the edge of the unpolished part of the high carbon steel sample 2, and the height of the polishing rod 4 is lowered.

[0044] Step 8: Turn on the electron beam emitting device and simultaneously rotate the polishing rod 4 at high speed.

[0045] Step 9: Repeat steps 6 to 8 to complete the polishing and grinding of the entire upper surface of the high carbon steel sample 2.

[0046] In an embodiment of the present invention, a machine tool can be installed inside the electron beam cavity, an XY-axis moving mechanism can be mounted on the machine tool, a lifting mechanism can be installed on the XY-axis moving mechanism, and the rotary drive mechanism can be installed on the lifting mechanism. The rotary drive mechanism drives the polishing rod 4 to rotate axially in the vertical direction. In this embodiment, the XY-axis moving mechanism can be a commonly used XY-axis linear drive module in the prior art, the lifting mechanism can be a conventional lifting mechanism such as a cylinder or a linear motor, and the rotary drive mechanism can be installed at the bottom end of the lifting mechanism. The rotary drive mechanism can be a servo motor, etc. The polishing rod 4 is mounted on the bottom output shaft of the rotary drive mechanism by a clamp.

[0047] In addition to the above embodiments, the XY axis moving mechanism can be installed on the top of the electron beam cavity, and then the lifting mechanism, the rotary drive mechanism and the polishing rod 4 can be installed in sequence. This structure is simpler than setting up a machine tool.

[0048] In an embodiment of the invention, the polishing rod assembly is a hollow assembly, which is equipped with a knob to seal its inner cavity. Before clamping the polishing rod 4, the knob of the polishing rod 4 is unscrewed to inject liquid dry ice into its interior, and then the knob of the polishing rod 4 is tightened. The polishing rod 4 is a hollow design, filled with dry ice, which allows for rapid solidification of liquid metal during polishing by relying on high supercooling, achieving a 10 6 -10 8 The cooling rate of ℃ / s significantly refines the grains on the sample surface.

[0049] In embodiments of the present invention, such as Figure 3 As shown, the distance between the polishing rod 4 and the electron beam gun 3 is 1.2-1.5 times the diameter of the lower beam spot 5 of the electron beam. Maintaining a suitable distance between the polishing rod 4 and the electron beam gun 3 ensures that when the polishing rod 4 polishes the surface of the high-carbon steel sample 2 that has been melted by the electron beam, the surface of the high-carbon steel sample 2 remains in a certain molten state, ensuring the polishing effect. Specifically, the lifting mechanism is installed at the top of the electron beam cavity and next to the electron beam gun 3 via an XY-axis moving mechanism, which allows for easy adjustment of the distance between the polishing rod 4 and the electron beam gun 3 according to parameters such as the lower beam diameter of the electron beam.

[0050] In an embodiment of the present invention, in step five, the electron beam machine is set with the following parameters: electron beam accelerating voltage of 60kV, focusing current of 390mA, accelerating current of 3-7mA, beam spot diameter of 5mm, and horizontal moving speed of stage 1 of 3-5mm / s; the rotational speed of the polishing rod 4 is 300-500r / min. Using these parameters ensures a polishing effect, resulting in a surface roughness Ra of less than 0.1μm after polishing.

[0051] This invention first uses a high-energy-density electron beam to melt the surface of a high-hardness sample, and then uses a high-speed rotating polishing rod 4 to fully fill the depressions with molten metal in a slightly molten state. The polishing rod 4 is hollow and filled with dry ice, which allows for rapid solidification of the liquid metal during polishing due to high supercooling, achieving a hardness of 10. 6 -10 8 The cooling rate of ℃ / s significantly refines the grain size on the sample surface. Furthermore, the bottom surface roughness Ra of the polishing rod 4 is approximately 0.05 μm, resulting in a surface finish far superior to that achieved after electron beam polishing. This process is suitable for high-hardness steel materials. By first melting and then polishing in a liquid state, a mirror-like polishing effect with zero material removal and loss can be achieved, with a surface roughness Ra of less than 0.1 μm after polishing.

[0052] In the description of this invention, it should be understood that the terms "center," "length," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "inner," "outer," "circumferential," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the system or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0053] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0054] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0055] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electron beam melting composite grinding method for improving the surface finish of high-carbon steel, characterized in that, Includes the following steps: Step 1: Install a polishing rod on the rear side of the electron beam gun inside the electron beam cavity via a lifting mechanism, and install a rotary drive mechanism for driving the polishing rod to rotate axially in the vertical direction. The polishing rod is a hollow polishing rod with a knob to seal its inner cavity. Before clamping the polishing rod, unscrew the polishing rod knob, inject liquid dry ice into it, and then tighten the polishing rod knob. Step 2: First, pre-treat the high carbon steel sample to be ground. The pre-treatment includes: using a wire cutting machine to process the high carbon steel to be ground into a cubic block shape, and then cleaning the high carbon steel sample in kerosene to remove various residual oil stains on the surface. The pretreated high-carbon steel sample to be ground is placed on the stage inside the electron beam cavity, and then the stage clamp is tightened to fix the high-carbon steel sample. Step 3: Use a vacuum pump to evacuate the vacuum chamber of the electron beam machine; Step 4: Adjust the observation window to align the electron beam gun tip with the corner of the high-carbon steel sample, and simultaneously lower the height of the polishing rod. Step 5: Set the parameters of the electron beam machine as follows: electron beam accelerating voltage is 60kV, focusing current is 390mA, accelerating current is 3-7mA, beam spot diameter is 5mm, stage horizontal moving speed is 3-5mm / s, turn on the electron beam emitting device, and at the same time make the polishing rod rotate at high speed, the polishing rod rotation speed is 300-500r / min; Step 6: Adjust the horizontal movement of the stage along the X-axis to achieve horizontal polishing. The polishing rod rotates and polishes the polished part of the high carbon steel sample. The rotation speed of the polishing rod is 300-500 r / min. Step 7: After the polishing of a section of the high carbon steel sample in the X-axis direction is completed, raise the polishing bar, the stage moves the high carbon steel sample back to its original position, and then the stage moves the high carbon steel sample in the Y-axis direction so that the electron beam gun is facing the edge of the unpolished part of the high carbon steel sample, and lower the height of the polishing bar. Step 8: Turn on the electron beam emitting device and simultaneously rotate the polishing rod at high speed, with the polishing rod rotating at 300-500 r / min. Step 9: Repeat steps 6 to 8 to complete the polishing and grinding of the entire upper surface of the high carbon steel sample, so that the surface roughness Ra after polishing is less than 0.1 μm.

2. The electron beam melting composite grinding method for improving the surface finish of high-carbon steel according to claim 1, characterized in that, In step three, the vacuum level of the electron beam machine vacuum chamber is 6×10⁻⁶. -2 Pa.

3. The electron beam melting composite grinding method for improving the surface finish of high-carbon steel according to claim 1, characterized in that, In step one, the distance between the polishing rod and the electron beam gun head is 1.2-1.5 times the diameter of the lower electron beam.

4. The electron beam melting composite grinding method for improving the surface finish of high-carbon steel according to claim 3, characterized in that, In step one, the lifting mechanism is installed in the electron beam cavity via an XY axis moving mechanism.

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